Configure XDM to accept remote logins

Question

How can I configure XDM server to accept remote X login and works as X server, which Configuration should be done on the clients if they want to connect to this X server?

Answer 1

To allow XDM remote logins you can do following:

1. Edit file: /etc/X11/xdm/Xaccess

change(uncomment) line:

# *                       #any host can get a login window

to:

*                         #any host can get a login window

and change(uncomment):

# * CHOOSER BROADCAST #any indirect host can get a chooser

to:

* CHOOSER BROADCAST #any indirect host can get a chooser

2. Edit /etc/X11/xdm/xdm-config

change(comment) line:

DisplayManager.requestPort:    0

to:

!DisplayManager.requestPort:    0

3. Restart XDM

On client machine start the Xorg server like this (assuming that you have already X running on :0):

X :1 -query ip_address

This will bring XDM to your display at display :1 and now you can login and work on client machine as you are logged directly to the server and switch between local and remote X with Alt + Fxx.
For Windows clients (I have never tested.) you can check Xming.

As XDMCP is using the below ports and make sure these ports are open in firewall:

• XDMCP 177 UDP
• X11 protocol 6000-6005 TCP
• xfs: X font server 7100 TCP

Consider allowing remote XDMCP session for public addresses is not very secure. You can think using it through VPN or over SSH.

Different distributions might require additional files to be configured, for example in openSUSE 13.1 /etc/sysconfig/displaymanager following value should be set to YES:

DISPLAYMANAGER_REMOTE_ACCESS="yes"